Various constraints in the design of meters that employ wireless radio transmitters and/or receivers restrict the type, size, and orientation of antennas that can be used in the metering devices. Such constraints include orientation and space restriction of meters. For example, a large portion of electricity meters are oriented vertically in a socket on a wall of a building. It is desirable to limit the size of the meter so that the meter does not extensively protrude from the wall on which it is located. It is also desirable to vertically mount printed circuit boards within the meter. The size constraint of limiting the outward protrusion of the meter from a wall coupled with the constraint of vertically mounting printed circuit boards within the meter makes it difficult to implement a conventional dipole, monopole, or loop antenna into a housing of such meters.
Another design constraint is a requirement that the antenna produce vertically-polarized electric fields in order to create effective omni-directional radiation coverage patterns. The internal implementation of conventional, vertically-polarized antennas with metering circuitry in a meter results in unfavorable consequences due to the close proximity of the antenna and the metering circuitry. For example, low gain and poor coverage patterns may result in such a situation where monopole, dipole, or loop antennas are incorporated.
Yet another constraint that may be encountered in the design of meters employing wireless capabilities is that external antennas are not practical, making the implementation of an internal antenna a necessity. External antennas may be easily implemented for metering devices but are extremely dangerous if human contact is encountered due to the high potential of service lines. Furthermore, external antennas are susceptible to unwanted tampering and accidental damage.
Problems with cross-talk and interference from electronic circuitry typically require separation and electrical isolation of the electronic circuitry from the ground and power planes of the printed circuit assembly. In order to accomplish the electrical isolation, separate assemblies are needed, which increases the size of the device incorporating the circuitry.
Accordingly, there is a need for the internal incorporation of an antenna into a metering device containing wireless functionalities without altering or adversely affecting the orientation or size of the metering device and for providing an effective omni-directional radiation coverage. The present invention satisfies one or more of these needs as well as other needs.